As for Leia’s words, I took it that every Skywalker has Vader in them, Ben (and Luke) included.
This is part of why I think Ben will die in the next movie. There’s obviously a viscous cycle here. The chain needs to be broken.
Well maybe on the first but I disagree on the second. I don’t think Skywalkers are necessarily more inclined to the dark, note that Luke says Rey basically has that same potential.